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Extreme “glacial cooling” that occurred more than a million years ago in southern Europe is likely to have caused an “extinction of early humans” on the continent, according to new research.
The previously unknown ice age pushed the European climate to “beyond what archaic humans could tolerate” and likely wiped out human life on the continent temporarily, concluded an academic paper published in the journal Science.
The findings by 11 researchers from institutions including University College London and the University of Cambridge challenge the long-held idea that humans have continuously occupied Europe since first arriving in the region.
The newly discovered cooling event was “comparable to some of the most severe events of recent ice ages”, said the paper’s lead author Vasiliki Margari from UCL. “We suggest that these extreme conditions led to the depopulation of Europe,” the researchers concluded.
Glacial-interglacial cycles, or warmer and colder periods each lasting thousands of years, have occurred cyclically over the past 2.6mn years, with large ice sheets forming during the colder spells and melting during the warmer periods.
According to the academic paper, a previously unknown glacial period that occurred about 1.1mn years ago led to abrupt cooling that lasted about 4,000 years. This happened as conditions began to warm and large ice sheets melted into the Atlantic Ocean, which pushed down European sea and land temperatures.
The researchers identified the glacial period using an analysis of marine micro-organisms and muddy sediment taken from deep under the ocean’s surface near the coast of Portugal. They then used computer models to assess how suitable the colder environment would have been for early human occupation.
Early humans, who may not have been able to build fires or create sufficiently warm clothing or shelters, would have been “very unlikely to have survived” the extreme cooling, said Chronis Tzedakis, a co-author of the paper from UCL.
Much colder and dryer conditions on land would have threatened the survival of various plants and animals, with winter temperatures remaining “freezing” for long stretches of time, added Tzedakis.
Sea surface temperatures in the region would have fallen below 6C, the paper found. The daily average sea surface temperature for the north Atlantic between 1979 and 2023 was 21C, according to the Copernicus Climate Change Service.
The paper also highlighted that there is a lack of archaeological evidence for the presence of early humans in Europe for the period between 900,000 and 1.1mn years ago, which could indicate that none inhabited the region for thousands of years following the cooling event. The oldest known human remains in Europe date from about 1.4mn years ago.
Although the earth’s climate has changed over time, man-made warming and the resulting weather extremes are occurring at a much faster pace.
Glacial-interglacial cycles historically occurred on “longer timescales” and were “quite different from changes [occurring] now”, said Tzedakis. “We can’t draw lessons from the past because it’s not directly comparable.”